* Velocity is a vector quantity, meaning it has both magnitude (speed) and direction. The direction of an EM wave can change when it enters a new medium, leading to refraction (bending).
* Speed is the magnitude of velocity, representing how fast something is moving. When an EM wave enters a new medium, its speed changes due to interactions with the medium's atoms and molecules.
Here's a breakdown of why the speed changes:
1. Interaction with Matter: EM waves are made of oscillating electric and magnetic fields. When they encounter a medium like glass or water, these fields interact with the charged particles (electrons) in the medium's atoms.
2. Absorption and Re-emission: The electrons absorb energy from the EM wave, get excited, and then re-emit the energy as a new wave. This process takes a tiny amount of time, causing a slight delay in the propagation of the wave.
3. Reduced Speed: The combined effect of absorption and re-emission results in the wave traveling at a slower speed in the medium compared to its speed in a vacuum.
Important Points:
* Vacuum Speed: The speed of light in a vacuum (c) is the fastest speed an EM wave can achieve. It's approximately 299,792,458 meters per second.
* Index of Refraction: The ratio of the speed of light in a vacuum to the speed of light in a medium is called the index of refraction (n). A higher index of refraction means the wave travels slower in that medium.
* Frequency Remains Constant: While the speed and wavelength of an EM wave change in a medium, its frequency (the number of waves passing a point per second) remains constant.
Let me know if you'd like more details on any specific aspect!
